A commonly used magnetic position detection device of the related art has a structure in which a magnetosensitive element formed of a Hall element or a magnetoresistive element is arranged so as to be opposed to a magnetized scale formed of N poles and S poles that are alternately arranged with fixed lengths λ.
Then, a change of a magnetic field at the time when the magnetosensitive element moves relative to the magnetized scale is read to detect a relative position between the magnetosensitive element and the magnetized scale.
In such a magnetic position detection device of the related art, substantially sinusoidal output signals with a period of the monopole length λ, which are output when the magnetosensitive element moves relative to the magnetized scale, are converted into pulse signals and counted, to thereby detect the relative position between the magnetosensitive element and the magnetized scale at a position detection resolution of the monopole length λ(see, for example, Patent Literature 1).
In Patent Literature 1, the position detection resolution comparable with the monopole length λ of the magnetized scale can be obtained. However, an existing magnetizing device has a limitation on magnetization of N poles and S poles to the magnetized scale, and a practical limit value of the monopole length λ of the magnetized scale is approximately 100 μm.
In an actual case, however, if the monopole length λ is excessively reduced, the magnetic field formed by the magnetized scale is weakened, and hence even when the monopole length λ is larger than the above-mentioned limit value, the magnetosensitive element cannot detect the monopole length λ. As a result, there is a problem in that the position detection resolution cannot be improved to be higher than a magnetic pole limit length λ0 determined by the magnetic pole material and the magnetosensitive element to be used.
One method for solving the problem described above is to arrange eight magnetosensitive elements and process each output of the magnetosensitive elements by a logic circuit, to thereby obtain a pulse signal with three periods when the magnetosensitive element moves by the monopole length λ (see, for example, Patent Literature 2).
Further, as another magnetic position detection device of the related art, a magnetic gear (magnetic scale) is used instead of a magnetized scale, and a change of a magnetic field formed by the magnetic gear and a magnet is measured by a magnetosensitive element, to thereby detect a relative rotation of the magnetic gear (see, for example, Patent Literature 3).